Polyester resins and epoxy resins can be used together if you let the previous batch dry thoroughly. For example, using thickened epoxy to fill a hole in your polyester laid-up sailboat.

When trying to get a bond to wood I've had much better success with epoxy and I think everyone else has, too. Bonding glass on glass, though, is a great use for polyester because you can use the mat. Mat makes a great bond from new to old and between layers of new. When laying up new glass to old use mat first (binding new to old), then cloth. Each successive layer will be in sets of two: mat, cloth; mat, cloth.

If you plan on putting gel-coat on the finished product this is another example of when to use polyester instead of epoxy. Gel-coat adheres better to poly, since it is poly.

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